Vibration and sound damping material



Oct. 13, 1942. E. A. w0RM, fJ

VIBRATION AND SOUND DAMPING MATERIAL Original Filed Aug. 2 s,- 1937 glwuqnm Z; 4.40

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Patented Oct. 13, 1942 UNITED STATE s PATENT orrl-ca VIBRATION AND SOUND DAMP'ING MATERIAL Erwin A. Worm, Jr., Oswego, N. Y;, assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Original application August 3, 1937, Serial No. 157,161. Divided and this application January 31, 1939, Serial No. 253,738

Claims. (Cl. 154-44) This invention is a division of my co-pending application, Serial No. 157,161, filed August 3. 1937, and relates to vibration and sound dampin materials, and more particularly to vibration and sound damping materials produced from felted fibrous sheets.

Felt and felted products, with or without waterproofing o r binders, have been used as sound damping and sound absorbing agents in connection with vibratile metal sound producing and transmitting surfaces, such for example as file cabinets, oflice furniture, vehicular and automobile bodies, machinery pads, partition and wall constructions, and generally wherever a relatively .cheap, easily applied material may advantageously be employed to reduce or inhibit the production or transmission of sound. Felt as produced by the usual water laying methods has not been entirely satisfactory for, such uses in that the fibers of the water-laid sheet tend to be predominantly oriented along the length of the sheet as produced on the machine, resulting in a polarizing of the flexibility characteristics of the material, in which state, the material customarily fed across tensioning rolls 3 and 4 and a guide roll 5 to the nip of differentially driven rolls 6 and'l, and thence through differentially driven rolls 8 and 9, l0 and H, and i2 and I3, to a wind-up indicated generally at M. Rolls -|,-'9,

II and iii are driven faster than rolls 6, 8, l0

and I2 with which theya-rev respectively paired.

A lubricant is applied to the surface of rolls I and 9 by means of wicks 45 dipping into troughs H5 in which a suitable lubricant such as kerosene is maintained to the required level. As a result of this arrangement, the felt-web 2 follows the slower moving rolls 6, 8, l0 and I2 and a slip results between the felt web 2 and the faster moving rolls 1, 9, II and I3. I have found that the lubricant applied to the surface of the fast moving rolls by the wicks 15 does not prevent the felt from following the slow moving rolls which,

succeed the lubricant application and press on the lubricated surface, but in the absence of the lubricant, the heat generated by the slip between the felt web and the fast moving-rolls results in and yielda satisfactory commercial product.

suitable for'use as a vibration and sound dampat their points of contact to generally stifien and ing and absorbing material is produced with a high degree of uniformity with respect to vits flexing properties both in directions parallel and normal to its length and in a much softer, less boardy, condition than is customarily available in unindented and noncorrugated sheets.

As an example of my invention, I produce a felted fibrous sheet which is preferably predomistickin'g and tearing of the felt when sufllcient pressure and differential speed exists to obtain the optimum effect. I have found that with a series of, four pairs of rolls, as diagrammatically illustrated, the difierence between the surface speeds of the rolls in each set may be from. 10% to 15% of the speed of the fastest pair of'rolls,

The manipulation of the sheet is done after the waterproofing ingredient, such as asphalt or flux;

oil, has been put into the sheet, for theefiect of such partial saturation is to bind the fibers strengthen the sheet and if the waterproofing ingredient is first put into thev sheet the distortion and softening effected by the differential working treatment permanently characterizes the 40 sheet after such treatment. If the sheet is nantly rag fiber, on a paper machine, which felt when dried and finished the usual way -is in the neighborhood of 3 thick and of the order of 1% pounds per square yard, being somewhat less dense than roofing felt. This sheet is rendered water resistant by the addition of asphalt or flux oil in such amounts that the voids of the sheet are not completely filled, as, for example, is commonly done in flooring felts.

After the asphalt or fiux oil has cooled from the usual saturating temperatures, I treat the sheet as diagrammatically illustrated in the accompanying drawing in which a felt sheet 2 is treated to the differential working prior to saturation, or partial saturation, the effect is temporary and subsequent saturation or partial saturation locks the fibers to a relatively stifier structhe drawing that the under surface of the web 2 isflrst engaged by the high speed roll I; then the upper surface by the high speed rolls 9 and H and finally the under surface is reengaged by high speed roll [3 to effect the final working.

' Thus each fiat surface of the web is independent-- ly engaged so that mechanical working of one surface of the sheet is effected in one position and working of the other surface of the sheet, while effected simultaneously, is effected on a longitudinally spaced portion of the web, as distinguished from theaction obtainable by feeding a web through a pair of rolls operating at a materially lower surface speed than the speed of travel of the web therethrough. I V

.I prefer to employ smooth faced rolls so that the final sheet exhibits a plane face. My differential working treatment results in opening or expanding of the sheet, and the formation of pores, as well as the further opening of pores present in the unsaturated sheet, so that the flnished treated material presents a surface requir ing a minimum amount of adhesive to secure it to a surface to be treated, possesses pores for the escape of solvents of such adhesive, if the adhesive be of the solvent type, and, although While I have illustrated and described the present preferred embodiment of my invention, it will be understood that'it may be otherwise practiced and embodied within the scope of the following claims.

I claim:

1. A vibration dampening material for application to vibratile metal sound producing and transmitting surfaces comprising a felted, fibrous, water-laid web having impregnating medium disposed within the body thereof but not completely saturating the same, said impregnating medium serving to stiffen and strengthen the web, said web exhibiting a substantially symmetrical flexibility in directions parallel and normal to its length and having expanded opposite surfaces, the expanded opposite surfaces of the web containing inwardly extending, artificially formed pores over substantially their entire areas.

2. A vibration dampening material for application to vibratile metal sound producing and transmitting surfaces comprising a felted, fibrous, water-laid web having a solidified impregnant disposed within the body thereof and serving to rapid and the treating material must be possessed of a high degree of ability to conform to angular androunded surfaces. The flexibilizing effect of the differential stretching andworking, without defacing, indenting or corrugating the sheet, results in a superior vibratile damping and sound absorbing material requiring a minimum of adhesive for complete bonding to the surface to be treated.

The reason for the softening effect obtained by the treatment I have described is not entirely feet, and has the undesirable effect of perma nently reducing the thickness of the sheet resulting in a more dense product with decreased vibratile vibration damping 'and sound absorbing properties. The degree of pressure which I prefer maintained between the rolls is such that the felt is firmly pressed in the nip of the rolls but the thickness of the sheet is not permanently decreased more than in the neighborhood of 5% or 6% of its thickness before treatment. I believe that the softening eflect is due to a crowding of the felt by each of the higher speed rolls into a nip through whichit can travel only-at the speed of the complementary slower speed roll, result-,

ing in an intense working of the felt. ,I do not wish to be limited to any particular theory of operation, for whatever action takes place in my treatment, .the result is a surprising increase instifien and strengthen the same, said impregnant being present in insuificient proportion to completely saturate the web, said web exhibiting a substantially symmetrical flexibility in directions'parallel and normal to its length and having opposite expanded planar surfaces presenting artificially formed pores over substantially their entire areas.

3. A vibration dampening material for application to vibratile metal sound producing and transmitting surfaces com-prising a felted, fibrous, water-laid web rendered water resistant by the presence of asphalt therein to stiffen and strengthen the same, said asphalt being present in insuflicient proportion to completely fill the voids of the web, said web exhibiting a substantially symmetrical flexibility in directions parallel and normal to its length and having expanded opposite surfaces, the expanded opposite surfaces of the web containing inwardly extending, artificially formed pores over substantially their entire areas.

4. A vibration dampening material for appli-- cation to-vibratile metal sound producing and transmitting surfaces comprising a felte'd, fibrous, water-laid web exhibiting a substantially symmetrical flexibility in directions parallel and norme] to its length and containing a solidified impregnant to stiffen and strengthen the same, said web having opposite expanded planar surfaces presenting artificially formed pores over substantiallytheir entire areas.

5. As a new article of manufacture for vibration damping and other uses where porous surfaces are desired, a felted, fibrous, water-laid web having a congealed, thermoplastic impregnating medium disposed within the body thereof but not completely saturating the same, said impregnating medium serving to stiffen and strengthen the web, said web exhibiting a substantially symmetrical flexibility in directions parallel and normal to its length and having expanded opposite surfaces, the expanded opposite surfaces of the web containing inwardly extendthe flexibility and conformability of the product,

ing, artificially formed pores over substantially their entire areas.

. ERWIN A. WORM,-.Js. 

